THz electrodynamics of mixed-valent YbAl and LuAl thin films

D. Barbalas; S. Chatterjee; D. G. Schlom; K. M. Shen; N. P. Armitage

doi:10.1140/epjb/s10051-021-00191-y

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2024 Impact factor 1.7

Condensed Matter and Complex Systems

Eur. Phys. J. B (2021) 94: 186
https://doi.org/10.1140/epjb/s10051-021-00191-y

Regular Article - Solid State and Materials

THz electrodynamics of mixed-valent YbAl $_{3}$ and LuAl $_{3}$ thin films

D. Barbalas¹^a, S. Chatterjee²^,3, D. G. Schlom⁴^,5^,6, K. M. Shen²^,5 and N. P. Armitage¹^e

¹ Department of Physics and Astronomy, The Johns Hopkins University, 21218, Baltimore, MD, USA
² Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, 14853, Ithaca, New York, USA
³ Department of Electrical and Computer Engineering, University of California, 93106, Santa Barbara, CA, USA
⁴ Department of Materials Science and Engineering, Cornell University, 14853, Ithaca, New York, USA
⁵ Kavli Institute at Cornell for Nanoscale Science, 14853, Ithaca, New York, USA
⁶ Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489, Berlin, Germany

^a dbarbalas@jhu.edu
^e npa@jhu.edu

Received: 7 June 2021
Accepted: 25 August 2021
Published online: 22 September 2021

Abstract

We present our results from time-domain THz spectroscopy measurements of thin films of mixed-valent YbAl $_{3}$ $$_3$$ and its structural analogue LuAl $_{3}$ $$_3$$ . Combined with Fourier transform infrared (FTIR) spectroscopy, the extended Drude formalism is utilized to study the quasiparticle scattering rate and effective masses in YbAl $_{3}$ $$_3$$ . We find that LuAl $_{3}$ $$_3$$ demonstrates conventional Drude transport whereas at low temperatures YbAl $_{3}$ $$_3$$ demonstrates a renormalized Drude peak and a mid-infrared (MIR) peak in the conductivity, indicative of the formation of a mass-enhanced Fermi liquid (FL). In YbAl $_{3}$ $$_3$$ the extended Drude analysis demonstrates consistency with FL behavior below the FL coherence temperature $T^{*} < 40$ $$T^* < 40$$ K with the scattering rate following $T^{2}$ $$T^2$$ proportionality and a moderate mass enhancement. Despite not observing a clear $ω^{2}$ $\omega ^2$ Fermi liquid-like frequency dependence the evidence is consistent with a moderate mass Fermi liquid, albeit one with a smaller mass than observed in single crystals. The extended Drude analysis also demonstrates a slow crossover between the FL state and the normal state above the $T^{*}$ $$T^*$$ in YbAl $_{3}$ $$_3$$ , indicative of incoherent hybridization effects persisting to high temperatures.